2.6 Protein stability in rat plasma
The stability of the prepared compounds was assessed in rat plasma collected from adult male Sprague Dawley (SD) rats, as previously described (Zhou et al. , 2017). Briefly, plasma was stored at -80 °C until needed. In vitrostability of FGF2 and PEG-FGF2 conjugates was measured using initial concentrations of 1000 ng·mL-1 of each protein in mouse plasma at 37 °C. Aliquots of 100 μL of plasma were removed at 0, 2, 4, 6, and 8 h time points and subjected to solid phase extraction on a Waters Oasis HLB 96-well plate (Milford, MA). The dynamic levels of FGF2 or PEG-FGF2 conjugates in the plasma were measured by human FGF2 immunoassay ELISA kit (Abcam, Cambright, UK) using a standard curve.